Sorry my first post is a question, but I have a problem with my focus.

It's a 2003 Focus Zetec Estate with a 1.8 TDCI (115).

It seems to have a loss of power over 3000rpm. It only happens when the engine is up to temperature and under load. It happily boosts up to 3000rpm and feels powerful, but from then on its like driving through custard.

It feels like the engines holding back at full throttle, sometimes it will hesitate and stutters it's way up to the redline. Other times it will just struggle to climb up the revs. From cold it flies to the redline. And it only happens over 3000rpm.

I had the fuel pump done as it felt like it was underfueling. Diagnostics threw up the crankshaft sensor but that has now been sorted. No other faults are showing. I've also tried some fuel additive and given it an Italian tune up. Nothing has helped so far.

There's just the one filter. It should last a bit more than 5000 miles but you could have had some dirty fuel from somewhere which has clogged it. When you change the filter check the housing for cracks and make sure the fuel lines are secure as air could be getting in. It certainly sounds like you have some sort of fuel delivery problem.

it rises steeply untll a little over 3k, then its basically goes "flat" - and thats a car in good condition, probably almost new, yours is 10 years old, the interooler will be clogged up with oil from the breather, your inlet manifold will be all choked up from the EGR system

So it may not be fuel related at all - or if it is - it could be the inectors

It may be the engine is being "choked" (the "breathing" is being restricted) -

Presumably you have changed the air filter (i do mine every 6 months or 6k)

So if you take off the intercooler, clean it out with petrol, and take the inlet manifold off and clean all the carbon/ muck uot of it, that may "fix" it

I recommend you fit an EGR blanking plate (solid, stainless steel) this will prevent the inlet from being clogged up again, and help the performance, economy and reliability of the car (a bit) - many FOC members have blocked their EGR valves now

The exhaust can also get choked (especially if the engine smokes a lot) the cat can get glogged - the italian-tune up helps

Cheap, pattern fuel filters can restrict the flow of the fuel - better with a Genuine Ford or "premium"/ quality branded filter

If the above does not work you can always get a remap, decat, etc (the engine can be mare surprisingly powerful) or just change up at 3k - (keep it in the powerband - between 2k & 3k) because its never going to rev like a racing motorcycle engine

There's just the one filter. It should last a bit more than 5000 miles but you could have had some dirty fuel from somewhere which has clogged it. When you change the filter check the housing for cracks and make sure the fuel lines are secure as air could be getting in. It certainly sounds like you have some sort of fuel delivery problem.

Yeh I guess it would be worth doing again. I will get that done this week. I always use decent branded fuel as well as I've heard bad things about supermarket diesel.

it rises steeply untll a little over 3k, then its basically goes "flat" - and thats a car in good condition, probably almost new, yours is 10 years old, the interooler will be clogged up with oil from the breather, your inlet manifold will be all choked up from the EGR system

So it may not be fuel related at all - or if it is - it could be the inectors

It may be the engine is being "choked" (the "breathing" is being restricted) -

Presumably you have changed the air filter (i do mine every 6 months or 6k)

So if you take off the intercooler, clean it out with petrol, and take the inlet manifold off and clean all the carbon/ muck uot of it, that may "fix" it

I recommend you fit an EGR blanking plate (solid, stainless steel) this will prevent the inlet from being clogged up again, and help the performance, economy and reliability of the car (a bit) - many FOC members have blocked their EGR valves now

The exhaust can also get choked (especially if the engine smokes a lot) the cat can get glogged - the italian-tune up helps

Cheap, pattern fuel filters can restrict the flow of the fuel - better with a Genuine Ford or "premium"/ quality branded filter

If the above does not work you can always get a remap, decat, etc (the engine can be mare surprisingly powerful) or just change up at 3k - (keep it in the powerband - between 2k & 3k) because its never going to rev like a racing motorcycle engine

Thanks for the help.

It hasn't always been like it. Only in the last few thousand miles. Engines done 70k.

Air filter was done 5000 miles ago so that will be another thing I order this week.

I have read about the egr. Mine isn't smokey but I will be blanking it off to see if it helps. Does an egr valve work through the rev range or is it only open lower down?

I will also try and clear all the deposits in the manifold, inter cooler etc.

1.5mm is a bit thin, in my opinion, but is probably ok for plates that are not close to the exhaust.

It is still worth cleaning out the the inlet manifold (by taking it off) as it is liable to be full of carbon / gunge

The sellers spiel is fairly accurate (of course its "dummed down" for a mass audience) exept the (working) EGR system only reduces emmisions when the car/ engine is new, when it is older, once the EGR system has contaninated the inlet, oil, etc etc causing more smoke and poorer MPG, so can have a worse effect on the enviroment than if it had not been fitted at all

A thirstier car can have a worse effect on the enviroment because of the impact producing/ refining/ transporting the extra fuel - even if the actual emmisions are higher - so MPG is important

Resetting the ECU can help after fitting an EGR plate

EGR systems are different on different engines, some work through the rev range at part or trailing throttle, some only at specific revs, even the types that only open at low revs/ on part throttle can produce flat spots or lag/ poor throttle response at some revs that are often eliminated when a solid plate is fitted